What uniquely identifies a row in a table? a. Index b. Column c. Primary key d. Tuple

Selected columns are removed from a table using a relational database's "select" method.It's possible that I'm mistaken.

MySQL CREATE TABLE students (  id INT PRIMARY KEY,  first_name VARCHAR(50),  last_name VARCHAR(50),  age INT,  major VARCHAR(50),  faculty VARCHAR(50)); CREATE TABLE location (  id INT PRIMARY KEY,  name VARCHAR(50),  rooms INT); CREATE TABLE faculty (  id INT PRIMARY KEY,  name VARCHAR(50),  department_id INT); 4. Find the number of employees in each department who get no commission or have salary less than5000.5. Find the maximum salary of employees in each department that the employee was hired 15 yearsbefore now. *hint: user TIMESTAMPDIFF(<unit type>,<Date_value 1>,<Date_value 2>), the unitcan be YEAR, MONTH, DAY, HOUR, etc...6. Find the last name of all employees that were not hired on Tuesday *hint: (UseDATE_FORMAT() function amd the format you need is %W, also use UPPER()7. Find the number of employees in each department who have a manager.8. Find the number of employees for each manager whose employees' minimum salary is greaterthan 5000.9. Find the number of…

What is the maximum number of columns you can define as a primary key when using the column-level approach to creating a table? ( refer to the tables in the JustLee Books database).                                                              a. 0 b. 1 c. 30 d. 255

How do you add a column to an existing table in MySQL?   a. MODIFY TABLE table_name ADD COLUMN new_column CHAR(3);     b. MODIFY TABLE table_name ADD new_column CHAR(3);     c. ALTER TABLE table_name ADD new_column CHAR(3);     d. ALTER TABLE table_name ADD COLUMN new_column CHAR(3);